1. Field of the Invention
The present invention relates to an aluminum-based alloy foil for use as negative electrodes of electrolytic capacitors. More particularly, the present invention relates to an aluminum-based alloy foil for such use, the foil having a high capacitance, and an increased mechanical strength, and being safe from cracks which otherwise would occur during the forging process. Hereinafter the electrolytic capacitor will be referred to merely as capacitor. The percentage is represented by weight unless specified to the contrary.
2. Description of the Prior Art
In order to minimize the size of capacitors without trading off their ability it is essential to increase the capacitances of not only anode foils but also negative electrode foils, hereinafter the negative electrode will be referred to merely as electrode. Conventionally the electrode foils are elecrochemically or chemically etched so as to increase the surface area thereof, thereby enhancing the capacitance per unit volume. In addition the compact capacitors requires a thin foil. However a thin foil is fragile, so that it must be strong enough to withstand any external stress.
To meet such demands in the industry the inventors have provided an improved aluminum-based alloy electrode foil, which is disclosed in Japanese Patent Publication (examined) No. 60(1985)-35815. According to the prior invention the alloy contains 0.01 to 1.0% of Ni, 0.1 to 1.0% of Cu, the balance being substantially aluminum.
The prior invention has increased the capacitance and mechanical strength of the foils. However a disadvantage is that cracks are likely to occur during the forging process of a slab.